Wednesday, May 30, 2007

The Mars Reconaissance Orbiter's HiRISE imager and the Mars Odyssey's THEMIS IR imager worked together to confirm these are caves--dark during the day, cooler than sunlit surfaces during the afternoon (but still warmer than surface shadows), warmer at night. These are huge skylights--over 300ft in size, and they overhang, meaning the cave is bigger than the skylight. The caves found are all big, partially because the THEMIS imager has a resolution limit of 100m, so they couldn't use it to refine candidate holes found in the visible HiRISE data. The diameters of the caves were from 100 to 252 meters.

One of the caves, on the northeast flank of Arsia Mons:

They were all found on the slopes of Arsia Mons, the southernmost Tharsis volcano. A global view here; it's the circular blob in 5 o'clock position from the center. These caves are likely the result of lava tubes, formed when lava cools on the surface and emptying out below.

On one of the seven skylights, they saw the floor lit; this allowed them to calculate the depth of the cave at 130 meters. The lit cave is shown below.

As Cushing, Titus, Wynne, and Christensen wrote in their conference paper, these caves offer sanctuary from all sorts of radiation, both UV and cosmic rays, that exist on the surface of Mars and would be the primary limiter of life at Mars. The caves' existence is enough to spring to life the imagines of the unseeable world inside of them; we will likely never know the wonders of what they contain in our lifetimes. It is unfortunate that they are currently only known on the slope of a Tharsis volcano--high in the thin Martian atmosphere, we are limited in our ability to land a spacecraft there easily.

Tuesday, May 22, 2007

As mentioned a few posts ago, galaxy cluster CL0024 bends space-time in a particular manner which shows a unique signature from its dark matter distribution. The press release image used ghostly blue as the mapping choice. Perhaps a more interesting way is showing the distortion of graph paper behind the cluster, from the LSST site:

Monday, May 21, 2007

I've been running the geiger counter nearly continuously for a year and a half--since December 1st, 2005. It's down today because we are going to build a cloud chamber at the Ryerson Astronomical Society meeting tonight, and I'd figure we'd have some other detectors there as well.

When you see this image in the popular media, be sure to realize it's a statistical map of the distribution of dark matter around a galaxy cluster _superimposed_ on an image of the cluster. It's not an image of dark matter. The actual image is this one:

By looking at the blue arcs in the image, astronomers can map how the massive galaxy cluster bends light from a more distant galaxy behind the cluster, and compare that distribution with what they see in the visible.

Here's a crop of the upper-left section of the cluster--you can see distorted images of a blue, star-forming, possibly spiral galaxy. The paper will probably have a reconstituted image of the lensed galaxy.

It's unfortunate that many people will see the blue image and think Hubble directly imaged some dark matter. The more important detail of the science was the ring shape and the proposed physics behind the shape from galaxy interactions.

Saturday, May 12, 2007

Can you argue for northeastern transplants to California, Arizona, and Miami setting the default as soda? What about St. Louis? Why is Nevada such a heterogeneous place? (My bet is lack of data). See the original project here: http://popvssoda.com:2998/

Wednesday, May 02, 2007

Last December four members of the RAS were lucky enough to spend four days at the MMT/Fred L. Whipple Observatory located on Mt. Hopkins south of Tucson talking to researchers and observers. One of the systems located at the "Ridge" area of the mountain was HAT, the "Hungarian-made Automated Telescope", a collection of small scopes there at Mt. Hopkins and in Hawaii. Gaspar was too busy working to talk to us, but we now know why. The collabration has discovered a huge exoplanet orbiting HD 147506, an eight-magnitude star 441 light-years away in the constellation Hercules. It's about an eight-Jupiter mass planet in an eccentric short 5.63 day orbit around a hot F8 star, and it's as dense as a terrestrial-style planet! It was discovered because from Earth, its orbit crosses the face of the star. The next transit is tomorrow morning (from here in North America).